Correlation Of Two Stroke “Two Volume” Scavenging Models With Test Data

It is well known that the use of “two volume” scavenging models, where the cylinder is idealized as two volumes with gas exchanged between them, represents a substantial improvement over the “perfect mixing” scavenging model for the computer simulation of two stroke engines. This is especially true during the early stages of the scavenging process, when scavenge ratio is low. It is shown that a simple, closed form relationship exists between the “stripping off” factor, Y, used in two volume scavenging models and the variation in scavenge efficiency with scavenge ratio.. A method is presented for estimating Y at low scavenge ratios using existing correlations of scavenge efficiency with scavenge ratio. This should make it possible to construct very good two volume scavenging models using only existing published data. Such models would be able to simulate in cylinder and exhaust gas conditions during the early stages of scavenging.